U.S. patent application number 11/355219 was filed with the patent office on 2006-08-31 for radio frequency identification of tagged articles.
Invention is credited to Eduard Levin.
Application Number | 20060192655 11/355219 |
Document ID | / |
Family ID | 36931496 |
Filed Date | 2006-08-31 |
United States Patent
Application |
20060192655 |
Kind Code |
A1 |
Levin; Eduard |
August 31, 2006 |
Radio frequency identification of tagged articles
Abstract
The RFID system is for automatic recognition of each one or all
of a plurality of objects located within an interrogation zone. It
is applicable for stock-taking or control of goods such as food.
The objects provided with tags having transponders carrying RFID
codes individually are sequentially scanned and activated one by
one. Interrogation signals are transmitted to the tags based on the
reader antennas and the configurations and locations of the tags.
Signals returned from the transponders of the tags are processed
for recognizing the locations of the selected tags and the
electronic contents of the tags. The operation continues until the
recognition and location of all tags in the entire interrogation
zone have been completed.
Inventors: |
Levin; Eduard; (Thornhill,
CA) |
Correspondence
Address: |
DAVID W. WONG
46 WILLOWBROOK ROAD
THORNHILL
ON
L3T 4W9
CA
|
Family ID: |
36931496 |
Appl. No.: |
11/355219 |
Filed: |
February 16, 2006 |
Current U.S.
Class: |
340/10.2 ;
340/10.1; 340/572.1; 340/8.1 |
Current CPC
Class: |
G06K 7/0008 20130101;
G01S 13/825 20130101; G01S 15/74 20130101; G01S 17/74 20130101 |
Class at
Publication: |
340/010.2 ;
340/825.49; 340/572.1 |
International
Class: |
H04Q 5/22 20060101
H04Q005/22 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2005 |
CA |
2,497,629 |
Claims
1. A method for the identification and location of radio frequency
identification RFID tags having configurations and locations,
comprising: forming signals for activating selected RFID tags,
based on reader antennas and said tags configurations and
locations; transmitting signals for activating of said selected
RFID tags in an interrogation zone of a reader; receiving signals
for activating said selected RFID tags in said interrogation zone
of a reader; processing signals for activating said selected RFID
tags in said interrogation zone of a reader to determine if tags
must be activated; forming a signal to operate transponder of an
activated tag; transmitting a RFID transponder signal from said
activated tags to a reader; receiving a RFID transponder signal by
said reader; processing an RFID transponder signal by said
reader.
2. A method according to claim 1 wherein includes the steps of
selecting location and coordinates of said interrogation zone of
said reader; selecting dimensions of tag zone equal to dimensions
of said tag; selecting of a start point of scanning of said
interrogation zone of said reader; calculation of signal parameters
for activation of tags for each tag zone; calculating time required
for scanning said each tag zone; creating of signals for activating
selected RFID tags in accordance with calculated signal signal
parameters for each said tag zone; transmitting activation signals
for activating said selected RFID tags; receiving said activation
signals for said selected RFID tags in said tag zone; processing
said activation signals for activating said selected RFID tags in
said tag zone and determining activation of a selected tag;
transmitting a signal information by a transponder of an activated
tag; receiving said signal information by said reader; said
processing a RFID transponder signal including processing said
signal information by said reader and reading said tag information;
creating a tag data consisting of tag coordinates, an electronic
code, description of product whereon said tag is provided, and
other information data; entering of said tag data in a RFID reader
memory; calculating time lapse between beginning of signal
transmission for activating said selected RFID tags and a present
time; comparing said time lapse with time of scanning in said tag
zone; shifting to a selected next tag zone location, when said time
lapse is more than said time of scanning of said tag zone;
repeating above steps until scanning operation of the entire said
interrogation zone has been accomplished; organizing, storing and
monitoring tag data including coordinates, electronic codes,
description of articles bearing said tags, graphic view of said
articles, security and service information data.
3. A method according to claim 2 wherein a number of scanning
operation of said tag zone is predetermined, and said scanning said
tag zone is repeatedly in accordance with said predetermined number
of scanning operation.
4. A method according to claim 3 wherein a tag zone is set in a
selected center of said interrogation zone of said reader, and
scanning is repeated by increasing dimensions of said tag zone in
number of times according to a value optimizing probability of tag
detection, identification of its electronic code and determination
of tag location, until tag information signal is received by said
reader.
5. A method of claim 2 wherein said signals activating said
selected RFID tags are pulses with fixed RF carrier having an
amplitude shift key (ASK), said received signals are demodulated at
said tag locations, and signal envelopes are processed in sequence
in a plurality of channels including a first channel for receiving
an initial signal, a second channel for receiving a second signal
delayed by a specific time from said initial signal, and a third
channel for receiving a third signal delayed by twice said specific
time wherein said specific time is dependent on an antenna aperture
and tag zone locations, and said number of channels is equal to
number of antennae, and said signal envelopes are compared with a
duplicate of said signal envelopes by time of matching, and an
actuation signal for turning on said transponder is created when
said signal envelopes and duplicate of said envelopes in all said
first channel, said second channel and said third channel
correspond with one another simultaneously, said actuation signal
turns on said transponder for transmitting information signal by
transponder.
6. A method according to claim 2 wherein said signals for
activating said selected RFID tags are pulses with own RF carrier
of amplitude and frequency shift keying (AFSK) and said received
signals at said tag locations are amplified and mixed, and RF
filtered for creating signal envelopes, and said signal envelopes
are detected and compared with duplicate signal envelopes by time
of matching, and an actuation signal is created for turning on said
transponder when said signal envelopes and duplicate signal
envelopes corresponds with one another in all said first channel,
said second channel and said third channel simultaneously, said
actuation signal turns on said transponder for transmitting
information therefrom.
7. A method according to claim 2 wherein said signals for
activating said selected RFID tags are pulse train with RF carrier
having amplitude shift keying (ASK) and a number of pulses is
predetermined, and said received signals at said tag locations are
processed with a plurality channels in a sequence with an initial
signal is first received in a first channel, and a second signal is
received in a second channel delayed by a specific time, and a
third signal received by a third channel delayed by twice said
specific time wherein said specific time is dependent on an antenna
aperture and said tag zone, and number of plurality of channels is
equal to the number of antennae, pulse train of envelopes of
signals for activating of said selected RFID tags is created in
each of said channel, said pulse train of envelopes are compared
with one another by time of matching, and the matching number of
pulses is calculated, and said matching number is compared with
said predetermined number of pulses for creating an actuation
signal to turn on said transponder when said calculated number of
pulses matches with said predetermined number of pulses whereby
said actuation signal turns on said transponder to transmit said
information signal.
8. A method of claim 2 wherein said signals for activating of said
selected RFID tags are pulse with RF carrier and quasi-random
envelope, and said received signals at said tag locations are
processed with a number of a plurality of channels sequentially
with a first signal received in a first channel, a second signal
received in a second channel and delayed by a specific time, and a
third signal received in a third channel and delayed by twice said
specific time wherein said specific time is dependent on an antenna
aperture and a tag zone, and said number of plurality of channels
is equal to the number of antennae, and signals are compared
between themselves with correlating, a positions of top peak of
cross correlation function are estimated for each couple of
signals, and an actuation signal of turning on said transponder is
created when the positions of top peaks of cross correlation
function for each couple of signals between couples by time of
matching are corresponding with one another whereby said actuation
signal turns on said transponder to transmit information signal
therefrom.
9. A method according to claim 2 wherein said signals for
activating of said selected RFID tags are pulses with fixed RF
carrier having amplitude shift keying (ASK), said received signals
at said tag location are demodulated for signal envelopes creation,
and time intervals between envelopes of said signals are provided
with clock pulses with every interval between said clock pulses
counted, and compared between one another and with a specific
number calculated by dividing a time interval between activating
pulses for an infinite tag location by interval between clock
pulses, and an actuation signal for turning on said transponder is
created upon under correspondence of all numbers whereby said
actuation signal turns on said transponder for transmitting
information signal therefrom.
10. A method according to claim 9 wherein said specific time delays
for said tag information signal received by reader antennas are
calculated for each antennae in accordance with location of tag
interrogation zones, and information signals from tags received by
said reader is delayed by said specific time in each reader
antennae, and delayed signals are summed up whereby overall signal
is processed by said reader.
11. An apparatus for identification and location of a plurality of
RFID tags, comprising: means for forming signals for turning on
selected RFID tags; means for transmitting signals for activating
of said selected RFID tags in an interrogation zone of a reader;
means for receiving signals for activating said selected RFID tags
in said interrogation zone of said reader; means for processing of
signals for activating of said selected RFID tags in said
interrogation zone of said reader to determine if tags to be
activated; means for forming signals to operate RFID transponder of
an activated tag; means for transmitting RFID transponder signals
to said reader; means for receiving an RFID transponder signals by
said reader; and means for processing an RFID transponder signals
by said reader.
12. An apparatus according to claim 11 wherein said means for
forming signals for turning on said selected RFID tags comprising:
means for selecting of location and coordinates of an interrogation
zone of said reader; means for selecting dimensions of a tag zone;
means for selecting of a start point of scanning of interrogation
zone of said reader; means for calculating parameters of signals
for turning on of said selected RFID tags for each said tag zone;
means for calculating time of scanning of said tag zone; means for
creating of signals for activating said selected RFID tags in
accordance with calculated signals parameters for each said tag
zone; means for transmitting signals for activating said selected
RFID tags; means for receiving said signals for activating said
selected RFID tags; means for processing said signals for
activating said selected RFID tags in said tag zone and to
determine activation of a present tag being interrogated; means for
transmitting an information signal by transponder of an activated
tag; means for receiving said information signals by said reader;
said means for processing said selected RFID with transponder
signal by said reader including means for processing said
information signals by said reader and reading of tag information;
means for creating of tag data consisting of tag coordinates,
electronic code of said tag, and description of product bearing
said tag and other related data; means for entering said tag data
into memory of said RFID reader means for calculating of time
passed from the beginning of transmitting of said signals for
turning on said selected RFID tags up to present time; means for
comparing of time passed from the beginning of radiating of signals
for turning on said selected RFID tags up to present time with time
of scanning of said tag zone; tag zone location to a next tag zone
location, when time passed for shifting passed from the beginning
of transmitting of signals for turning on selected RFID tags is
more then time of scanning of said tag zone, means for repeating
above steps of signals for turning on selected RFID tags and
information signals creation, transmission, receiving and
processing until scanning of the entirety of said interrogation
zone of said reader is completed; means for organizing, storing and
monitoring tag data; means for providing said RFID tag with power
supply.
13. An apparatus according to claim 12 including means for scanning
said tag zone for a predetermined number of times.
14. An apparatus according to claim 13 including means operativ for
calculating dimensions of said tag zone, and means operative for
controlling scanning of said and tag zone within said
dimensions.
15. An apparatus according to claim 14 wherein said means for
providing RFID tag with power supply include means for transmitting
a RFID tag power supply signal to a selected RFID tag.
16. An apparatus according to claim 14 wherein said means for
providing RFID tag with power supply includes means for supplying
power signals for activating selected RFID tags.
17. An apparatus according to claim 14 wherein said means for
providing RFID tag with power supply includes means for supplying
said tag with power from a built-in battery.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to systems of maintaining the
inventory of objects provided with radio-frequency transducers such
as tags or transponders containing electronic codes for their
recognition. Such devices are commonly known as radio frequency
identification devices (RFID). More specifically, this invention
relates to radio-frequency methods of spatial resolution of tags,
RFID tag and tag activation device. A RFID consists of a reader and
transponders; the latter are affixed on objects which are subject
to inventory and are located in a storage such as a warehouse.
[0003] 2. Description of Prior Art
[0004] RFID methods and systems provide the recognition of objects
with identification tags affixed thereon. The process of tag
recognition must be accomplished at high speed and with minimum
error. In this process it is necessary to determine the tag
location or direction relative to a reader.
[0005] Each RFID consists of a reader and a transponder with the
latter affixed on the object subject to inventory. Readers are
provided for primarily reading tag codes and, some of them,
searching for tag direction only. The reader transmits a tag
activation signal for all tags in the interrogation zone
simultaneously, and adjusts the activation signal which has been
sent in advance to the tags with known codes. Tags activated in
such a manner transmit response signals which carry information of
tag electronic codes. These signals reach the reader practically
simultaneously. For a small number of tags, for example, from one
to five, because of the differences in electronic circuit
parameters, tags are activated in an insignificant time lag, which
allows a reader to read codes by activating tags repeatedly in
order to increase the probability of codes recognition. When a
larger number of tags are to be read by the readers, tag signals
reach the reader practically simultaneously, which may result in
failure to recognize the objects with adequate accuracy.
[0006] It is also very important to authenticate the tags in
reading the memory content of each tag when a plurality of tags are
located in the tag interrogation zone simultaneously. The RFID
HANDBOOK by Klaus Finkenzeller, Carl Hansen Verlag, Munich/FRG,
1999 outlines four methods of solving the problem of space,
frequency, code and time discriminations in RFID. U.S. Pat. No.
6,600,443 and U.S. Pat. No. 6,476,756 both to J. A Landt, and U.S.
Pat. No. 6,069,564 to R. Hatano et al illustrate methods and
systems of tag reading and determination of its direction. Both
U.S. Pat. No. 6,600,443 and No. 6,476,756 to J. A. Landt illustrate
a method of tag signal structure analysis while U.S. Pat. No.
6,069,564 by R. Hatano et al proposes a multi-directional RFID
antennae for this purpose.
[0007] U.S. Pat. No. 6,034,603 to W. E. Steeves and U.S. Pat. No.
6,354,493 to J. Mon show technical solutions for reducing the
probability of recognition error on the basis of selecting RFID tag
search criteria, generation feedback signals according to the ratio
of RFID tags matching the search criteria to the total number of
RFID tags received.
[0008] U.S. Pat. No. 2,452,351 to H. L. Bloxom et al and Canadian
Patent No. 2,437,888 describe tag reader systems and tag control
and reading algorithms of signal processing for one or several
readers.
[0009] Canadian patents No. 2,447.975 to P. M. Eisenberg et al, and
No. 2,399,092, and No. 2,450,189 both to P. A. Sevcik et al
describe aspects of collection and use of data obtained by RFID tag
interrogation, in particular, by comparing information obtained
through interrogation of tags with the data recorded during
repeated interrogations.
[0010] U.S. Pat. No. 6,317,028 to C. Valinlis, U.S. Pat. No.
5,822,714 to R. T. Cato, U.S. Pat. No. 6,034,603 to W. E. Steeves
and Canadian patent No. 2,447,975 to P. M. Eisenberg et al show
RFID systems of tag recognition for the case of a plurality of
radio frequency identification tags. To effectively recognise tags,
a number of other technical solutions assume a tags' data base as
previously known and perform its current status control through
comparison of the read current values with the data of a base as
shown in U.S. Pat. No. 5,822,714 to R. T. Cato. U.S. Pat. No.
6,034,603 to W. E. Steeves also shows such a method and system of
tag construction with improved tag interference avoidance in which
a tag includes both a receiver module and a processor, while the
generation of a signal is decided as a result of analysis of radio
frequency activity.
[0011] All of the above prior art patents fail to teach, or even
suggest, any RFID method and system possessing features which can
perform a recognition and locating functions in case of a plurality
of objects, and reading the codes and locating tags of both single
decoding or working simultaneously with large numbers of articles,
under conditions of locating the inventory objects on the plane or
in the random volume with minimization of errors caused by
reflection of signals from surrounding surfaces.
SUMMARY OF THE INVENTION
[0012] The principal object of the present invention is to provide
recognition systems with radio frequency identification devices
(RFID) and, more specifically, to provide radio frequency methods
of three-dimensional tag selection, creation of tag activation
devices and their algorithms as well as tag design.
[0013] The read range of the reader is determined according to
dimensions of an interrogation zone and a search starting point,
the tag's possible location is selected in the form of a small
spatial domain namely a local interrogation zone. The reader starts
transmitting tag activating signals through three spatially
separated omnidirectional antennae. The time of each signal
transmission is calculated in accordance with the tag's assumed
location, which is being entered into the reader's memory. The
signals are received by each of the tags, and only the tag for
which the reader signals are calculated and transmitted according
to the specific formulas, will be activated. The activated tag
emits its own identification signal which carries the information
about the individual tag code. This identification signal is
received by the reader and a tag code is selected and entered into
the reader's memory according to the preliminarily calculated tag
location. Following the tag's assumed location having been
selected, calculated, and entered into the readers' memory, the
next signal sequence transmission will be calculated and the
signals are transmitted through the reader's antennae, etc. The
entire sequence is repeated for scanning the entire interrogation
zone.
[0014] The invention possesses numerous benefits and advantages
over known RFID systems. In particular, the invention permits the
reduction of the time of search and recognition of tags when there
are large numbers of tags to be recognized within an interrogation
zone. It can locate each one of a plurality of objects and
increases the probability of reading the codes without error. Noise
immunity is increased due to the elimination of false responses
when receiving signals are reflected from random surfaces such as
the warehouse walls, shelves, adjacent articles, container
surfaces, etc. One embodiment of the invention can be used with
existing tags by providing only minor modifications of the input
stages of the existing transponders. It may be used in a
single-channel, or two-channel, or multi-channel systems. The
universal character of the system allows it to be used as a mobile
or a stationary device, as well as a two-dimensional or a
three-dimensional space version.
[0015] As a whole, the present invention resolves the complex
problem in object location and recognition both in cases of a
single decoding, as well as with a large number of articles
simultaneously located in an inventory object location in diverse
conditions; and it is applicable in a wide variety of fields in
manufacturing, shipping or storage.
[0016] The RFID method and system of the present invention are
based on the implementation of a Tag Activator for creating
specific signals which perform tag interrogation zone multi-step
scanning, selected transponder activation, and processing the
transponder signal by the reader for:
[0017] Determination of the total interrogation zone coordinates
and writing them into the reader memory; [0018] Determination of
local interrogation zone start point coordinates and writing them
into the reader memory; [0019] Calculation of activation signal
parameters for each reader antennae for assumed tag location, i.e.
local interrogation zone; [0020] Creating signals for tag
activation--a tag activator coder; [0021] Transmitting of signals
by reader antennas; [0022] Receiving of activation signals for
processing by the tag activator decoder and making a decision if
this tag supposed to be activated or not; [0023] Creation a control
signal by the tag activator decoder to activate transponder
transmitter and transfer the electronic code of the tag to a
reader; [0024] The selected tag signal has been received by a
reader, then the tag electronic code is retrieved from a signal and
memorized by the reader, and the reader's memory keeps the tag
coordinates, which are in fact the location of the object with a
tag; [0025] If in the course of time determined by search area
range no response signal has been received, then the following step
of search is performed by shifting the local interrogation zone on
the coordinate off one step, which is determined by tag activator
resolution; [0026] Procedure of activation signals creation,
transmitting and processing, tag signal receiving is repeated until
the total interrogation zone is completely examined; [0027] Tag
electronic codes, their location and other tag information are
indicated on the reader's data base and monitor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a layout of tags location and two antennae
transmitting the activating signals relating to concept of tag
activation according to an embodiment of the present invention.
[0029] FIG. 2 is the signals emitted by two antennae of tag
activator coder and received them by a tag relating to a concept of
tag activation according to an embodiment of the present
invention.
[0030] FIG. 3 is a block diagram of tag location decoder for a case
referring to according to an embodiment of the present
invention.
[0031] FIG. 4 is a layout of activated and non-activated tags and
antennae of tag activator coder according to an embodiment of the
present invention.
[0032] FIG. 5 is the signals transmitted by three antennae of tag
activator coder and received by tag activator decoder operating
according to concept of comparison of single pulses of the present
invention according to an embodiment of the present invention.
[0033] FIG. 6 is a block diagram of tag activator decoder operating
in accordance with the concept of comparison of single pulses
according to an embodiment of the present invention.
[0034] FIG. 7 shows a principle of localization and activation of
tags in total interrogation zone in two-dimensional Cartesian
coordinates according to an embodiment of the present
invention.
[0035] FIG. 8 shows a principle of localization and activation of
tags in three-dimensional Cartesian coordinates according to an
embodiment of the present invention.
[0036] FIG. 9 is the activating signals and tag activator decoder
pulse trains operating according to concept of comparison of time
intervals according to an embodiment of the present invention.
[0037] FIG. 10 shows the activating signals with different
frequency carrier according to an embodiment of the present
invention.
[0038] FIG. 11 is a block diagram of tag activator coder for
activating signals with different carrier according to an
embodiment of the present invention.
[0039] FIG. 12 is pulse train of activating signals according to an
embodiment of the present invention.
[0040] FIG. 13 is the activating signals for a case of tag
activation by pulses with randomized envelope according to an
embodiment of the present invention.
[0041] FIG. 14. is a block diagram of tag activator decoder for a
case of tag activation by pulse train according to an embodiment of
the present invention.
[0042] FIG. 15. is a block diagram of tag activator decoder for a
case of tag activation by pulses with randomized envelope according
to an embodiment of the present invention.
[0043] FIG. 16 is the signals transmitted by tag activator coder
with electronic access key according to an embodiment of the
present invention.
[0044] FIG. 17. is a block diagram of tag activator decoder with
electronic access key according to an embodiment of the present
invention.
[0045] FIG. 18 is a flow chart of a tag activator coder and reader
according to an embodiment of the present invention.
[0046] FIG. 19 is a block diagram of RFID Transponder with build-in
tag activator decoder according to an embodiment of the present
invention.
[0047] FIG. 20 is a block diagram of RFID reader with build-in tag
activator coder according to an embodiment of the present
invention.
[0048] FIG. 21 is a block diagram of Amplitude Shift Keying RFID
transponder with build-in tag activator decoder according to an
embodiment of the present invention.
[0049] FIG. 22 is a block diagram of Amplitude Shift Keying RFID
reader with build-in tag activator decoder according to an
embodiment of the present invention.
[0050] FIG. 23 is a block diagram of Amplitude Frequency Shift
Keying tag with build-in tag activator decoder according to an
embodiment of the present invention.
[0051] FIG. 24 is a block diagram of Amplitude Frequency Shift
Keying RFID reader with build-in tag activator coder according to
an embodiment of the present invention.
[0052] FIG. 25 is a block diagram of RFID transponder with build-in
ultrasound tag activator decoder according to an embodiment of the
present invention
[0053] FIG. 26 is a block diagram of RFID reader with build-in
ultrasound tag activator coder according to an embodiment of the
present invention
[0054] FIG. 27 is a block diagram of RFID transponder with build-in
light activated tag activator decoder according to an embodiment of
the present invention
[0055] FIG. 28 is a block diagram of RFID transponder with build-in
light activated tag activator decoder according to an embodiment of
the present invention.
[0056] FIG. 29 is a block diagram of Amplitude Shift Keying RFID
transponder with build-in tag activator decoder according to an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0057] With reference to the drawings, the procedure of the
activation of tags located within an interrogation zone is shown on
FIGS. 1 and 2. A tag can be located randomly in points, for
example, from Point 1 to Point 5, representing tags 1 to 5 locating
at these points on a flat surface in a two-dimensional
interrogation zone. If a tag is located at Point 1 and is
transmitting a signal, the latter signal 10 reaches the antenna 11
with time delay t.sub.D and is received by the antennae 11 and 12
with a time delay having a path length difference l.sub.21. This
path length difference is constant for any location of tags 1, 2 or
3, for example, on a hyperbolic curve 8.
[0058] Whereas in a reversed situation, namely, signals 14 and 15
are simultaneously transmitted by antennae 11 and 12 respectively,
the signal 15 from antenna 12 will reach any tag located on the
curve 8 with a delay of 1.sub.21/C relative to the signal 14, where
C is a signal propagation velocity in the given environment. But if
the signal 15 is transmitted by 1.sub.21/C earlier than the signal
14, then both signals will reach any tag 1, 2 or 3 simultaneously.
Here and after only signal envelopes for radio frequency signals
are shown.
[0059] When two signals 14 and 15 (in the form of pulses) are being
transmitted, the signal 15 will be transmitted by the delay time
(t.sub.o-t.sub.21) relative to signal 14, if the path 7> the
path 6, it indicates that the tags are located on the left of the
middle line 16 or with the delay (t.sub.o+t.sub.21), if the path
7<the path 6, it indicates that the tags are located on the
right of the line 16, where the paths 6 and 7 represent the
distances between the tag 1 and antennae 11 and 12 respectively,
wherein t.sub.o=d/C; and d is the distance 9 between the antennae,
and the duration T.sub.p the pulses 14 and 15 is selected from
T.sub.p<<t.sub.o for determining the system's range
resolution.
[0060] FIG. 2 shows the transmission of pulse signals 17 and 18
respectively from the antenna 12 for the tags 4 and 5. In such
event, if the difference between the times in which these signals
are received by tags 4 and 5 is equal to t.sub.o.
[0061] FIG. 3 shows the basic tag decoder in the system of the
present invention, it consists of a delay device 24 and an AND
circuit 25. Signals 14 and 15 enter the first input of the tag
decoder in a propagation time of t.sub.D through the antenna 11 to
the tag 1, and then the second input through the delay device 24 to
provide output signals 21 and 22 with the time delay of t.sub.o,
and due to the selected temporal relations, the AND circuit 25 will
create an output signal 23 at the moment when the first input has
received signals 19 and 20 from the second antenna, and the second
input has a signal from the first antenna with the time delay for
the period t.sub.o. The output signal 23 is used as the signal for
the activation of a tag located at any point of the hyperbolic
curve 8.
[0062] As shown in FIG. 2, the tags 4 and 5 are not located on the
hyperbolic curve 8. In such instance, the AND circuit 25 will not
produce the coincidence signal due to nonconformity of temporal
relations between the signals and, as a result, these tags 4 and 5
will not be activated. The positions of pulses 17 and 18 for tags 4
and 5 show that it would not able to activate these tags. For the
above reasons, two omni directional antennae would not provide a
single-valued local activation of tags located on the flat surface.
Therefore, to activate a tag located in a certain local
interrogation zone 1 on the flat surface by antennae 11, 12 and 13
as shown in FIG. 4, it is necessary to use all these three antennae
located along a straight line on the indicated flat surface,
although generally antennae can be located randomly in a certain
volume.
[0063] FIG. 4 shows that a tag will be activated at point 1 of a
flat surface which will the unique point of intersection of two
hyperbolic curves 8 and 26, where the curve 8 is determined by the
antennas 11 and 12, and the curve 26 is determined by the antennae
12 and 13 respectively. The temporal
relations between the activating signals 14, 15 and 33 from
antennas 11, 12 and 13 respectively are selected similar to the
case examined above for the two antennae as shown in FIG. 1 and
FIG. 3.
[0064] The operation of the deactivator at the antenna locations
shown in FIG. 4, is illustrated in FIG. 5. As shown, signals 14, 15
and 33 are transmitted by antennas 11, 12 and 13 respectively with
the delay relative to signal 14 for the time period
(t.sub.o-t.sub.21), if the delay periods D.sub.2>D.sub.1, or
(t.sub.o+t.sub.21), if the delay periods D.sub.2<D.sub.1.
Likewise signal 33 is transmitted with the delay relative to signal
14 for the time period (2 t.sub.o-t.sub.31), if D.sub.3>D.sub.1,
or (2 t.sub.o+t.sub.31) if the delay periods D.sub.3<D.sub.1.
The delay of signal 33 relative to signal 15 can be calculated in
the same manner.
[0065] FIG. 5 also shows pulse signals 34 received at point 1 in
FIG. 4 from antennas 11, 12 and 13, and the pulse signals 35
delayed by a time period of t.sub.o pulse signals 34, and pulse
signals 36 delayed by the time period of 2t.sub.o from pulse
signals 34. FIG. 6 shows the block diagram of the tag deactivator
for processing these signals from the three antennae. The
deactivator consists of an antenna 29, a preamplifier 30, a
demodulator 31, two time delay devices 24 which provide a time
delay period of t.sub.o, and an AND circuit 32. The pulse signals
34, 35 and 36 serially enter the first input, the second input and
the third input of the AND circuit 32 respectively. FIG. 5 shows
these signals coincide only at the moment t.sub.a with a resulting
signal 37 appearing at the output of the AND circuit 32. The signal
37 activates a tag transmitter of the tag located at point 1 in
FIG. 4. The group Signal 38 consists of pulses 14, 15 and 33. These
pulses reach the first input of the AND circuit 32 of another tag
located at point 4 in FIG. 4. On the other hand when group signals
39 and 40 are provided at the second and third inputs of the AND
circuit 32, the AND circuit 32 will not produce any output signal,
thus, no tag will be activated. Therefore, it is possible to
activate any tag in a total tag interrogation zone by changing
signal delays according to a specific rule well in advance at any
point on the surface bearing antennae and tags.
[0066] FIG. 7 shows the reader interrogation zone in the Cartesian
coordinates X and Y. To facilitate estimations, antennae 11 and 13
are placed symmetrically relative to the centre of the coordinates,
at which an antenna 12 is placed. In the general case, antennae can
be placed on the surface within the X and Y coordinates randomly.
The search area has, for example, the shape of a rectangle defined
by four points, namely point 60 (at coordinates -Rm, 0), point 53
(at coordinates -Rm, Rm), point 54 (at coordinates Rm, Rm), and
point 58 (at coordinates Rm, 0), where Rm is the Read Range; X and
Y are the coordinates of the present interrogation zone 57; X (55),
Y (56) are the steps of scanning on coordinates X and Y
respectively; d is the distance between the antennae; and
l.sub.31(27), l.sub.32(59), l.sub.21(10) are path length
differences of these signals.
[0067] Scanning of the Local interrogation zone (indicated by a
circle); is performed step-by-step starting from point 53 (-Rm, Rm)
with the step size on X axis determined by value X (the direction
shown by pointer). For signals transmitted by a tag activator coder
from reader in the form of amplitude-modulated pulse signals, for
example, the dimensions of local interrogation zone are dependent
on the pulse duration and it is determined by the range definition
X and Y.
Wherein X=Y.apprxeq.Tp.times.C.
D1, D2, D3 are distances from the antennas to the local
interrogation zone.
[0068] To calculate parameters of the activating signals and delay
times relative to each other, the following equations are used: D1=
(x+d).sup.2+(y).sup.2, D2= (x).sup.2+(y).sup.2, D3=
(x-d).sup.2+(y).sup.2; (1) t.sub.21=(D2-D1)/C; t.sub.31=(D3-D1)/C;
t.sub.32=(D3-D2)/C. (2)
[0069] To calculate greatest time interval of signal propagation
from reader to interrogation zone borders the following equations
are used: TR=(Rm.sup.2+Rm.sup.2)/C=Rm /2/C. (3)
[0070] To activate a tag in the three-dimensional coordinates as
shown in FIG. 8, it is necessary to use four antennas 11, 12, 13,
and 61 while hyperbolic curves 8 and 26 determine the activated tag
location in the X, Y plane, and the curve 62 determines the tag
location in the three-dimensional space X, Y, and Z.
[0071] The tag activation described above is based on using
activating signals in the shape of pulses. For the single-valued
activation of a tag, differences between other signal parameters as
frequency and phase can be used.
[0072] The main criteria of activation of a tag is the coincidence,
at a certain moment of time, of signals transmitted by a reader,
which have been previously selected according to the time,
frequency or to the phase of transmitting signals. A coincidence
must take place at a certain moment of time in the tag decoder.
[0073] Another method is by the comparison of time intervals
between signals received by tag from antennas 11 and 12, in which
the time of signal propagation between these antennas is
t.sub.o.
[0074] As shown in FIG. 9, signals 14, 15, and 33 transmitted by
antennas 11, 12, and 13 respectively. Signal 15 is transmitted with
the delay relative to signal 14 for the time (t.sub.o-t.sub.21), if
D2>D1 or (t.sub.o+t.sub.21), if D2<D1. Likewise signal 33 is
transmitted with the delay relative to signal 14 for
(2t.sub.o-t.sub.31), if D3>D1 or (2t.sub.o+t.sub.31), if
D3<D1; the group signal 34 are received from antennas 11, 12,
and 13 at point 1 of FIG. 4. The group signal 50 from clock
generator, filling the time interval between signals, is received
by the tag, from antennas 11 and 12 in which the group signal N1 is
received at the antenna 12 and the group signal N2 is received at
the antenna 13 respectively. As shown, these group signals N1 and
N2 coincide only for the tags located at point 1 of FIG. 4.
Thus, this coincidence is a main criteria of proper tags
activation.
[0075] For other tags, such as tag 4 of FIG. 4 for example, the
interval t* between signals arriving the tag from antennas 11 and
12 is not equal to interval t** between signals arriving the tag
from antennas 12 and 13, it means the number N1* is not equal to
number N2* respectively. At the same time, in order to avoid false
activation, the time intervals between signals received from
antennas 11 and 12, by the tag, 12 and 13 must be compared between
itself and by the interval t.sub.o as well.
[0076] Another method of tag activation when carrier frequencies of
activating signals are different in shown in FIG. 10 in which
Signals 63, 64, and 65 with carrier frequencies .omega.1, .omega.2,
.omega..sub.3 are transmitted by antennas 11, 12, and 13
respectively of FIG. 4. Delay times t.sub.21, t.sub.31 selected
according to the rule of scanning of the total interrogation zone,
for example, from left to right, from up to down as shown in FIG.
7. Then if tag is located in previously calculated zone with
coordinates X,Y. Signals with carrier frequencies .omega..sub.1,
.omega..sub.2, .omega..sub.3 to reach the tag simultaneously will
be sent to tag antenna 29 with delays t.sub.31 for signal 63, and
(t.sub.31-t.sub.21) for signal 64, and without delay for signal 65
as shown in FIG. 10. These signals are amplified by preamplifier 30
as shown in FIG. 11 and converted in frequency converter 66 with
heterodyne frequency .omega..sub.0. The sum of signals with new
frequences .omega..sub.1-.omega..sub.0,
.omega..sub.1+.omega..sub.0, .omega..sub.2-.omega..sub.0,
.omega..sub.2+.omega..sub.0, .omega..sub.3-.omega..sub.0,
.omega..sub.3+.omega..sub.0 pass through band-pass filters 67, 68,
and 69 respectively tuned on frequencies
.omega..sub.1-.omega..sub.0, .omega..sub.2-.omega..sub.0,
.omega..sub.3-.omega..sub.0. Each of these signals passes through
the envelope detector 70 and then is sent to the proper input of
AND circuit 32. When the signals enter the circuit 32
simultaneously, the output signal from the AND circuit will
activate the tag transmitter. For the tags which are not in point
to be considered the signals are not sent to their inputs
simultaneously because the delays t.sub.21 and t.sub.31 are
calculated separately for each local interrogation zone and they
differ from each other. So the AND circuits 32 of tag activator
decoder will not generate any activation signal and no signal will
be transmitted by the transponder.
[0077] In some cases it is necessary to use transponders protected
from unauthorized access. The modification of such systems is the
method described above. This is the way of tag activation using
differences in carrier frequency of activating signals transmitting
by reader antennae. The other possible options of similar system
are RFID systems with activating signals in the form of pulse train
or quasi-random signals. Similar systems possess the larger reader
range and interference protection because of increasing
signal/noise ratio in comparison with single pulse systems. FIG. 12
shows signals in the system with the transmission of the activating
signals in the form of a pulse sequence. The activating signal 14
consists, for example, of four pulses with the same or different
duration and transmitted by the first antenna 11 of FIG. 1. Signal
15 represents a copy of the first signal shifted for time
(t.sub.o-t.sub.21) and transmitted by antenna 12. Signals 19 and 20
represent the sum of signals from antennas 11 and 12 received by
tag activator decoder. This signal is sent to the direct input of
the AND circuit 25 of FIG. 3 and then sent to the second input of
AND circuit as well but delayed for time t.sub.o. Four pulses will
appear in serially in the output of AND circuit 25 of FIG. 3. A
block diagram of tag activator decoder for RFID system with
activating signals in the form of pulses train is shown in FIG. 14.
This block diagram is the development of tag activator decoder of
FIG. 6 and differs from it by the introduction of a pulse counter
71. If number of pulses calculated by a counter in the output of
AND circuit 32 concurs with the numbers of activating pulses from
the tag activator coder, then the transponder control circuit 108
will create a signal to initialize the tag transmitter.
[0078] FIG. 13 shows signals in the RFID system with the activating
signals in the form of quasi-random signals. The activating signal
14 represents, for example, harmonic signal modulated by randomized
amplitude of limited duration and transmitted by the first antenna
11 of FIG. 1 in which only signal envelopes are shown. Signal 15
represents a copy of the first signal displaced for time
(t.sub.o-t.sub.21) and transmitted by antenna 12. Signals 19 and 20
represent a sum of signals from antennas 11 and 12 received by a
tag activator decoder. Referring to FIG. 15 a block diagram of tag
activator decoder for RFID system with quasi-random signals is
illustrated. This tag activator decoder is similar to that shown
FIG. 6 and differs from with the addition of the controller 74 and
correlator 75. Signals 19 and 20 enter the input of signal
processor 73 of FIG. 15. The signal processor 73 performs an
analog-to-digital conversion of the input signals, and then
transfers them to the first input of the controller 74 which
transfers signals 19 and 20 to the first input of the correlator
75. Signals 21 and 22 are similar to signals 19 and 20 but delayed
for a time period of t.sub.o to be sent to the second input of the
correlator 75. A correlation function 76 as shown in FIG. 13 will
appear from the output of the correlator 75 after the signals 19,
20, 21 and 22 have been processed. The function 76 has a maximum
time of t.sub.m which corresponds to time (t.sub.R-t.sub.L)/2 in
which t.sub.R and t.sub.L are upper and lower borders of the time
interval between the end of signal 20 and the beginning of signal
21. Signals 19 and 20 enter interrogation zone with a time delay of
t.sub.o between signals 19 and 20, and signals 21 and 22 are
coincided respectively. The correlator 75 of FIG. 15 evaluates the
position of the maximum value of the correlation function 76 and
sends a signal to the transponder control circuit 108 to initiate
the tag transmitter. If a tag is located outside of the
interrogation zone then the maximum of the the correlation function
76 will be shifted to the left or to the right depending on the tag
position and the correlator 75 will not create and send signal to
initialize the tag transmitter.
[0079] Another embodiment of the present system is the provision
for protection from unauthorized access of the system with an
electronic key. An electronic access key is realized as as a system
that transmitting a specific signal to open the tag activator
decoder before activation signals are sent out. Key signal enters
the tag activator decoder in which it is compared with its
duplicate in the tag activator decoder memory. If the key signal
corresponds with the duplicate, the tag activator decoder will be
opened for activation signals processing otherwise the receiver is
locked.
[0080] FIG. 16 shows signals in the RFID system with electronic key
signals in the form of a pulse train 41. If the receiver of the tag
is opened by the key signal, a specific signal 42 is created to
open the tag activator decoder during the time interval t.sub.k
sufficient to receive and process activation signals 34 to 37.
[0081] FIG. 17 shows a block diagram of the tag activator decoder
with electronic key stages built-in. A pulse train 41 enters the
input of a pulse comparator 45 to compare with its duplicate. In
case of complete correspondence of the key signal with its
duplicate, the comparator produces an output signal to activate
circuit 46 that creates the signal 42. This signal 42 will open an
electronic switch 47 to pass the activation signals 34 to 37 and to
activate the tag transmitter as a result.
[0082] The overall operational algorithm of the RFID system of the
present invention is shown in FIG. 18. The system assumes the
technical parameters such as range R.sub.m, range definition X, Y,
location of antennae, and the speed of electromagnetic or
ultrasound wave propagation, are all known for establishing a rule
of scanning of total interrogation zone. The present algorithm
foresees a survey of the total interrogation zone according to the
rule: from left to right, from up to down as shown in FIG. 7. The
first step 77 of the algorithm operation is to turn RFID system on.
The next step 79 is entering the data of read range Rm, antenna
aperture d, wave propagation speed C, steps of scanning .DELTA.x,
.DELTA.y from a reader keyboard by the operator for calculating the
time interval of signal propagation to a maximum remote point of
interrogation zone T.sub.R according to formula (3) and the
parameter t.sub.o. Next step 80 is to set the total interrogation
zone boundaries, thereafter step 81 calculates the start point of
area scanning (-R.sub.m, R.sub.m). Step 85 calculates the ranges
D1, D2, and D3 from reader antennae to local the center of the
interrogation zone according to formulas (1). The time delay
t.sub.21 between signals 14 and 15 as shown in FIG. 5 is determined
by step 83. Depending on the proportion between D1 and D2 estimated
by step 84, a time delay t.sub.1 as shown in FIG. 5 between the
signals transmitted by antennas 11 and 12 is chosen and estimated
by steps 85 and 86. Similar delay t.sub.2 between signals 14 and 33
of FIG. 5 is estimated and calculated by steps 88, 89, 90 and 91.
The next step 93 is the creation of a pulse train to operate
transmitter signals of tag activator coder in accordance with the
calculated delays. The values of time delays are also used in the
reader intake for the creation of adaptive antenna consisting of
three separate antennae. In accordance with these values, it is
introduced a time shift between signals received by antennas 11,
12, and 13 to compensate the delays of the signals caused by
different time of propagation of these signals from the tag to each
antenna and, finally, to provide in-phase or coherent receiving of
tag signals to the reader. For example, a signal received by
antenna 2 shifts relative to the signal received by antenna 1 by
time t.sub.21, a signal received by antenna 3 shifts relative to
the signal received by antenna 1 by time t.sub.31 which creates a
reader coherent receiver. The steps 94, 95, and 96 evaluate the
time t.sub.D passed after the beginning of transmitting the
activating signal up to the current time and are implemented as a
timer for comparing time t.sub.D with a time t.sub.R relative to
the time of propagation of signals to maximum remote point of the
total interrogation zone. If after transmitting of the activating
signals by tag activator coder an answer signal from tag is not
received by the reader during the time interval t.sub.R, it means
that there is no tags in the survey local interrogation zone and
the next step in scanning of total interrogation zone would be
performed. The situation, in which tag signals received by reader
but the time of survey of interrogation zone is not expired, is
implemented by steps 94, 95, and 96. Then the scanning of zone
continues in the above order to receive a signal of other probable
tag or tags located in the same zone. Step 97 saves the tag
coordinates and its electronic codes for the creation of database,
monitoring of data and the item images of the display. Step 99
creates the next step of scanning the search area by increasing the
current meaning of coordinate X to the value .DELTA.X, after that a
control of program is transferred to the block 82 for organizing of
next cycle of scanning of the search area. If a new meaning of
current coordinate exceeded the bound of total interrogation zone
resulting from the analysis in step 100, step 98 will shift the
coordinate X to left in a distance with X=-Rm and the coordinate Y
will shift for one step down with a distance of Y=Rm-.DELTA.Y. Step
101 analyzes the current value of the Y coordinate. If this value
when shifted by a step .DELTA.Y became negative then the survey of
the search area is considered completed, and step 102 makes a
creation and ordering of database, data monitoring and printing.
Step 103 stops the RFID device after the total interrogation zone
is completely scanned. The above described steps 77-101 are
implemented by an arithmetic and logic program microprocessor in
the control loop.
[0083] Referring to FIGS. 19 and 20, a block diagram of RFID system
is illustrated. It consists of a RFID reader 105 and RFID
transponder 109 and a channel called tag activator for activating
the transponder. A tag activator coder 106 is implemented in the
reader 105 and a tag activator decoder 104 is implemented in a tag
to control the transponder 109. The reader for receiving the tag
information signal consists of an antenna 29, a controller 112
operating for transmission and reception of signals, creation of
control and information signals, data accumulation and monitoring,
signal processor 111, the reader receiver 110, the database 113 and
monitor 114 for storage and the display of digital, text and
graphic information about the transponders and the code, location
etc., of these components.
[0084] The tag activator coder 104 consists of a tag activator
controller 116, an activation signal former 117 and a transmitter
115. The tag activator controller 116 calculates the signal
activation parameters for creating signals in accordance with a
rule of total interrogation zone scanning to operate the
transmitter 115 and the transmit activation signals by the antennae
in the direction of activating tag.
[0085] Tag activator decoder 104 consists of an antenna 29, a
preamplifier 30, a demodulator 31 for obtaining a signal envelope,
a tag location decoder 107 for tag activation signals processing
and to create input signal if a tag is supposed to be activated. A
transponder control circuit 108 is provided for operating the
transmitter of the transponder 109 which is activated when the
transponder is connected to a battery with the operation of an
electronic switch. The output of the transponder 109 is connected
to an antenna for transmitting an information signal containing the
tag electronic code. Each transponder is provided with active power
supply such as a built-in buttery or a passive power supply 48. If
the transponder is within the range of the reader, a power supply
will be induced in the transponder antenna by the electromagnetic
or ultrasound field strength.
[0086] The transmitter 115 of tag activator coder, the activation
signal former 117, controller 116, the antenna 29, preamplifier 30,
demodulator 31, tag location decoder 107, transponder control
circuit 108, other elements of reader 105 and transponder 109 can
be implemented in analog hardware, digital hardware and software or
in their combination.
[0087] FIGS. 21-22 show a block diagram of RFID system which use
amplitude modulated signals, namely, single pulses as activating
ones named ASK--Amplitude Shift Keying System consisting of a RFID
couple of reader 105 and transponder 109, and a channel comprises
of two devices to activate the transponder, the tag activator coder
106 and the tag activator decoder 104. The operation of this system
is similar to that described above for FIGS. 19 to 20. But, in
addition to that described above, in this system the reader output
stages such as that from the omnidirectional antennae 29 and dual
directional couplers 118 are used to transmit activation signals
from the tag activator coder 106 outward to receive tag signals, as
well as to provide power to the tag transmitter. The dual
directional couplers 118 uncouples the transmitter and receiver,
compensating delay lines 119 for creating a coherent receiver of
transponder signals by control of signal delays, controller 112 for
controlling transmitting, receiving and creation of activation and
information data signals, and accumulation and monitoring of data.
The receiver 110 receives RF signal and sends it to the signal
processor and controller 112. A controller creates, operates and
monitors data consisting of digital, text and graphic information
from transponders in the database storage 113 and monitor 114. The
tag activator coder 106 consists of an activation signal former 117
and transmitter 115. The controller 112 calculates and creates
signals to operate signal former 117. Radio frequency signals from
former 117 enter transmitter 115 to radiate activating pulses
outward in accordance with rules of interrogation zone scanning.
The tag activator decoder 104 consists of antenna 29, preamplifier
30 of RF activating signals, demodulator of signals 31, delay lines
24 and control logic 25. The control logic 25 compares activating
signals as described above for that shown in FIG. 6. The control
logic 25 sends a signal to the transponder control circuit 108
which controls the transmitter of transponder 109 by operating, for
example, an electronic switch connecting the battery to transponder
to radiate information signal from the transponder outward to the
reader. Each transponder is provided with active or passive power
supply 48.
[0088] FIGS. 23-24 show a block diagrams of RFID system of the
present invention which use amplitude modulated signals, namely,
single pulses as activating ones with different carrier
frequencies, called AFSK--Amplitude and Frequency Shift Keying
System consisting of a RFID couple including reader 105 and
transponder 109 and a channel of transponder activation having tag
activator coder 106 and tag activator decoder 104. Reader output
stages such as omnidirectional antennae 29, dual directional
couplers 118 are used for transmitting activation signals from the
tag activator coder 106 outward, to receive transponder signals, as
well as to provide transponder transmitter with power. The reader
consists of compensating delay lines 119 that create a coherent
receiver of transponder signals by control of signal delays,
controller 112, signal processor 111, receiver 110, database 113
and monitor 114. Dual directional couplers 118 uncouple the
transmitter and receiver. In operation, the receiver 110 receives
the RF signal and forwards it to signal processor and controller
112. The controller 112 creates, operates and monitors data
including digital, text and graphic information from transponders
in the database storage 113 and monitor 114.
[0089] Tag activator coder 106 consists of activation signal former
117 and transmitter 115. Controller 112 calculates and creates
signals to operate the signal former 117. The former 117 generates
three pulses with different carrier frequencies and variable time
of transmitting in accordance with a total interrogation zone
location. Transmitter 115 sends the activating pulses to proper
antennae 29 to radiate them to a search zone. The tag activator
decoder 104 consists of antenna 29, preamplifier of RF for
activating signals 30, mixer 120, local oscillator 121, band pass
filters 67, 68, and 69, adder 122, envelope detector 70, control
logic 32, and transponder control circuit 108. Radio frequency
signals from the antenna 29 enter the preamplifier 30 input. Mixer
120 converts the carrier frequencies of the activating signals down
by mixing them with the signal from a local oscillator 121. Band
pass filters 67, 68, and 69 select and pass low frequency signals
in accordance with initial position of each activating signal from
the tag activator coder. Envelope detectors 70 create envelopes of
activating signals which are fed to the inputs of control logic 32
after summing it in the adder 122. The control logic 32 compares
the activating signals and create an output signal to control the
transmitter of the transponder 109 which is actuated by operating
an electronic switch for connecting a battery to the transponder so
as to radiate the information signal from the transponder outwards
to the reader. Each transponder is provided with active or passive
power supply 48.
[0090] FIGS. 25-26 show block diagrams of the RFID system of the
present invention, which uses amplitude modulated ultrasound pulses
as activating signals named This ultrasound embodiment consists of
a RFID couple including the reader 105 and transponder 109 and a
channel of transponder activation having tag activator coder 106
and tag activator decoder 104. The reader consists of at least one
radio frequency antenna 29, dual directional coupler 118,
controller 112, signal processor 111, receiver 110, transmitter
115, database 113 and monitor 114. The tag activator coder consists
of activation signal former 117, transmitter 125, pulse distributor
126 and an ultrasound transducers 127. In operation, the activation
signal former 125 creates activating pulses 14, 15, and 34 as shown
in FIG. 5 in accordance with commands from the controller 112 and
sends them to the transmitter 125. The pulse distributor 126
distributes activating signals to appropriate ultrasound
transducers 127 for transmitting them to tag interrogation zone.
The tag activator decoder consists of an ultrasound microphone 123,
preamplifier and band pass filter 124, envelope detector 71, delay
lines 24, control logic 32, and transponder control circuit 108.
The ultrasound microphone 123 receives ultrasound pulses and
converts them into electrical signals. Band pass filters and
amplifier 124 amplify and select activating signals, and the
envelope detector 70 creates activating pulse envelopes which are
fed to the inputs of control logic 32 after being delayed by the
delay lines 24. The control logic 32 compares activating signals
and creates an output signal for controlling the transmitter of
transponder 109 after actuating electronic switch for connecting a
battery to the transponder to radiate information signal from the
transponder outward to the reader. Each transponder is provided
with active or passive power supply 48. Another way to provide
transponder of ultrasound RFID system with power supply is to
obtain supply voltage 49 from the ultrasound microphone output 123.
The reader may include optionally a RF transmitter 115 to provide a
tag with power supply by induced electromagnetic radiation.
[0091] FIGS. 27-28 in combination shows a block diagram of a Light
Activated system (LA RFID) according to the present invention,
which uses amplitude modulated light pulses as activating signals.
The system consists of RFID couple having a reader 105 and
transponder 109 and a channel of transponder activation including
tag activator coder 106 and tag activator decoder 104. A reader
consists of at least one radio frequency antenna 29, dual
directional coupler 118, controller 112, signal processor 111,
receiver 110, transmitter 115, data base 113 and monitor 114. The
tag activator coder consists of activation signal former 117, pulse
distributor 131, and light generators 132. Activation signal former
117 for creating activating pulses 14, 15, 34 in accordance with
commands from controller 112 as shown in FIG. 5 and forwards them
to the pulse distributor 131. The pulse distributor 131 distributes
activating signals to initialize light emission of appropriate
light generator 132 for transmitting them to the tag interrogation
zone.
[0092] The tag activator decoder consists of receiver includes
photo sensor 128, amplifier 129, signal former 130, delay lines 24,
control logic 32, and transponder control circuit 108. A photo
sensor 128 receives light pulses and converting them into
electrical signals. An amplifier 129 amplifies the activating
signals and forwards them to the signal former 130. Former 130
operates as a low pass filter, for example, for creating activating
pulse envelopes, which are fed to the inputs of the control logic
32 after having been delayed at delay lines 24. The control logic
32 compares the activating signals to create an output signal for
controlling the transmitter of the transponder 109 by operating an
electronic switch for connecting the power supply battery to the
transponder. Each transponder is provided with an active or passive
power supply 48. Another way to provide transponder of Light
Activated RFID system with power supply is to obtain supply voltage
49 from photo sensor 128 which converts light into electrical
power. The reader may optionally include a RF transmitter 115 to
provide the tag with power supply by induced electromagnetic
radiation. This is a simple way to activate a selected tag by
merely sending a narrow beam of light at the tag location. Some
optional elements such as the pulse distributor 131, delay lines
24, control logic 107 can be omitted from the Light Activated RFID
System block diagram. Another logical device consisting of a
controller for comparing envelopes of signals for turning on
selected RFID tags by reference level must be provided in tag
activator decoder.
[0093] FIG. 29 shows a block-diagram of the tag activator decoder
for the above described RFID Reader as shown in FIG. 22, in which
the method of selective tag activation is provided by receiving
signals from reader antennas by a tag and comparing of time
intervals between signals and by specific interval. The tag
activator decoder 104 consists of an antenna 29, dual dual
directional couple 118 and receiver 133, including preamplifier of
RF activating signals and their demodulator, pulse generator 51,
electronic switch 52, controller 112, transponder control circuit
108, and transponder 109. The pulse generator 51 produces the clock
pulses 50 as shown in FIG. 29. The controller operates the
electronic switch 52 to create pulse trains N1 and N2 by opening
and closing depending on signals from the receiver 133. The
controller 112 compares the numbers of clock pulses N1 and N2
between itself and by interval t.sub.o as well and depending on
whether the numbers N1 and N2 correspond to each other and with
number N.sub.o (specific number calculated by dividing t.sub.o by
the interval between clock pulses), the controller 112 sends a
signal to the transponder control circuit 108. Circuit 108 controls
the transmitter of the transponder 109 such as by the operation of
an electronic switch for connecting a battery to the transponder to
radiate information signal from the transponder outward to the
reader. Each transponder is provided with active or passive power
supply 48.
[0094] It is to be understood that variations and modifications of
the present invention can be made without departing from the scope
of the invention. It is also to be understood that the scope of the
invention is not to be interpreted as limited to the specific
embodiments disclosed herein, but only in accordance with the
appended claims when read in light of the forgoing disclosure.
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